1. John Carelli, Instructor Kutztown University carelli@kutztown.edu

2. Awk (Programming/Scripting Language)
Features:
programmable
shares many constructs with “C”
… but has a number of extensions (ex: Associative Arrays)
interpreted
data-driven
designed for ease of use
Bell Labs (Aho, Weinberger, Kernighan)
Versions:
awk
gawk
nawk

3. awk [options] [program] [file-list]
Syntax:
awk [options] [program] [file-list]
awk [options] –f program-file [file-list]
Input text
Records
Fields
awk program
pattern { action }

4. Awk – default operation
Input processed one line at a time
Each line is a record
built-in variable $0
Each record is automatically parsed
Broken into tokens
Each token is a field
built-in variables $1 to $n
where n is the number of fields
default field delimiter is whitespace (\s)

5. Awk – basic program An awk program consist of pattern/action lines
syntax:
pattern { action }
patterns
Match using RegEx based commands on the current line
actions
If matched, perform some operation on the line

6. BEGIN
END
Expression
 ~
 !~

7. if (conditional) then action [ else action]
while (conditional) action
for (counter; conditional; increment) action
for (variable in array) action
do action while (conditional)
break
continue
variable = expression
print [list of expressions] [> expression]
printf format [,list of expressions] [> expression] -> a comma will print a space
next
exit
{list of statements}

8. FILENAME – name of the input file
NF – number of fields in the current line
NR – line number of the input stream
$0 – the entire line
$1 – first field of the current line
$2 – second field of the current line
$3, $4, etc. – rest of fields
FNR – record number in current file
FS – input field separator
OFS - output field separator

9. Awk commands (no single quotes)
awk –f
# Comments

10. Statements Expression String literals Assignment operator: =
Logical operators: || && !
Matching operators: ~ !~
Relational operators: < <=
Arithmetic operators: + - *
= = != > >=
/ % ^
Increment and decrement operators:
Parenthesis
String literals

11. int(num)
Returns integer portion of num
exp(num)
log(num)
sqrt(num)
length(str)
Length of the string
substr(str,pos,l en)
Returns substring of str that begins at pos for len characters
index(str1, str2)
Returns index of str2 in str1 or 0 if str2 is not present in str1
split(str, arr, del)
Places elements of str, delimited by del, in the array arr; Returns the number of elements in the array arr
printf and sprint
Similar to C
tolower / toupper

12. printf formatString, var1, var2, ….
C-style output formatting
- (before C++ stream objects)
printf formatString, var1, var2, ….
formatString formats listed variables in the order given
conversion specifiers get embedded in the formatString
conversion specifiers begin with %

13. printf – conversion specifiers
Basic Syntax:
% flags width [ . precision ] type
if flag is a minus sign, left justify
width is the character width of the output
padded, if necessary
precision (for floating point values)
basic types:
d for integers
s for strings
f (fixed) or e (scientific) for floats

14. Defintion
array[string-key] = value;
for (<elem> in <array>) <action>;

15. if / if-else
while
for
break
continue

16. Print each registrant, the conference and the amount due from conf
Print each registrant, the conference and the amount due from conf.data
Print company, name and conference for all registrants that don’t owe money
Print name and amount due for registrants attending the Coatings conference and that owe money
Previous example but print headings
Print the number of unique conferences being held

17. Write a program that calculates the average amount paid by all participants in the conf.data file. In addition, calculate the average amount owed by each participant, and print these values.
Write a program that calculates the amount that was paid by each registrant. For each registrant, print out the name of the registrant, the amount paid, and the average amount paid by all registrants.
Write a program that will print the number of registrants registered for the Adhesions conference, Coatings conference and Resins conference

18. Write a program using the conf.data file that does the following:
Calculate and print the number of people registered for conferences who come from Digital
Calculate and print the total amount owed for people from Digital
Calculate the average amount owed for registrants from Digital